U.S. patent application number 16/015189 was filed with the patent office on 2019-12-26 for configurable discovery reference signal periodicity for narrowband internet-of-things in unlicensed spectrum.
The applicant listed for this patent is TELEFONAKTIEBOLAGET L M ERICSSON (PUBL). Invention is credited to Oskar Drugge, Olof Liberg, Mai-Anh Phan, David Sugirtharaj, Emma Wittenmark.
Application Number | 20190394706 16/015189 |
Document ID | / |
Family ID | 68980430 |
Filed Date | 2019-12-26 |
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United States Patent
Application |
20190394706 |
Kind Code |
A1 |
Phan; Mai-Anh ; et
al. |
December 26, 2019 |
CONFIGURABLE DISCOVERY REFERENCE SIGNAL PERIODICITY FOR NARROWBAND
INTERNET-OF-THINGS IN UNLICENSED SPECTRUM
Abstract
In certain embodiments, a method of operating a wireless
communication device comprises receiving a narrowband secondary
synchronization signal (NSSS) in a discovery reference signal
(DRS), identifying a transformation applied to the NSSS, and
determining a DRS periodicity based on the identified
transformation.
Inventors: |
Phan; Mai-Anh;
(Herzogenrath, DE) ; Sugirtharaj; David; (Lund,
SE) ; Wittenmark; Emma; (Lund, SE) ; Drugge;
Oskar; (Hjarup, SE) ; Liberg; Olof;
(Stockholm, SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TELEFONAKTIEBOLAGET L M ERICSSON (PUBL) |
Stockholm |
|
SE |
|
|
Family ID: |
68980430 |
Appl. No.: |
16/015189 |
Filed: |
June 22, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04J 2011/0096 20130101;
H04W 52/0216 20130101; H04W 48/10 20130101; H04J 11/0076 20130101;
H04J 11/0073 20130101; H04L 5/0048 20130101; H04W 48/16 20130101;
H04W 48/12 20130101 |
International
Class: |
H04W 48/10 20060101
H04W048/10; H04J 11/00 20060101 H04J011/00; H04W 52/02 20060101
H04W052/02 |
Claims
1. A method of operating a wireless communication device,
comprising: receiving a narrowband secondary synchronization signal
(NSSS) in a discovery reference signal (DRS); identifying a
transformation applied to the NSSS; and determining a DRS
periodicity based on the identified transformation.
2. The method of claim 1, wherein identifying the transformation
comprises identifying a phase shift of the NSSS.
3. The method of claim 2, wherein identifying the phase shift
comprises determining the phase shift from among a predetermined
number of candidate phase shift values, and wherein the DRS
periodicity is determined from among a predetermined number of
candidate DRS periodicities according to the determined phase
shift.
4. The method of claim 3, wherein the predetermined number of
candidate phase shift values is four and the predetermined number
of candidate DRS periodicities is four.
5. The method of claim 1, wherein identifying the transformation
comprises identifying an orthogonal cover code (OCC) applied to the
NSSS.
6. The method of claim 5, wherein identifying the OCC comprises
determining the OCC from among a predetermined number of candidate
OCCs, and wherein the DRS periodicity is determined from among a
predetermined number of candidate DRS periodicities according to
the determined OCC.
7. The method of claim 6, wherein the predetermined number of
candidate OCCs is four and the predetermined number of candidate
DRS periodicities is four.
8. The method of claim 1, further comprising detecting a narrowband
physical broadcast channel (NPBCH) within a same DRS period as the
NSSS.
9. The method of claim 8, further comprising: identifying another
transformation applied to the NSSS; and determining a redundancy
version of the NPBCH according to the other transformation.
10. The method of claim 9, wherein the transformation is a phase
shift, and the other transformation is an orthogonal cover code
(OCC).
11. The method of claim 9, wherein the transformation is an
orthogonal cover code (OCC) and the other transformation is a phase
shift.
12. The method of claim 1, wherein the DRS is transmitted in
unlicensed spectrum.
13. A wireless communication device, comprising: processing
circuitry, memory and transceiver circuitry collectively configured
to: receive a narrowband secondary synchronization signal (NSSS) in
a discovery reference signal (DRS); identify a transformation
applied to the NSSS; and determine a DRS periodicity based on the
identified transformation.
14. The wireless communication device of claim 13, wherein the
processing circuitry, memory and transceiver circuitry are
collectively further configured to detect a narrowband physical
broadcast channel (NPBCH) within a same DRS period as the NSSS.
15. The wireless communication device of claim 14, wherein the
processing circuitry, memory and transceiver circuitry are
collectively further configured to: identify another transformation
applied to the NSSS; and determine a redundancy version of the
NPBCH according to the other transformation.
16. The wireless communication device of claim 13, wherein the
transformation is a phase shift or an orthogonal cover code
(OCC).
17. A radio access node, comprising: processing circuitry, memory
and transceiver circuitry collectively configured to: determine a
discovery reference signal (DRS) periodicity; apply a
transformation to a narrowband secondary synchronization signal
(NSSS) to be transmitted in a DRS, wherein the transformation
corresponds to the determined DRS periodicity; and transmit the
NSSS in the DRS.
18. The radio access node of claim 17, wherein the transformation
is a phase shift or an orthogonal cover code (OCC).
19. The radio access node of claim 17, wherein the processing
circuitry, memory and transceiver circuitry are further
collectively configured to: apply another transformation to the
NSSS, wherein the other transformation corresponds to a redundancy
version of a narrowband physical broadcast channel (NPBCH) to be
transmitted within a same DRS period as the NSSS.
20. The radio access node of claim 19, wherein the transformation
is a phase shift and the other transformation is an orthogonal
cover code (OCC).
Description
TECHNICAL FIELD
[0001] The disclosed subject matter relates generally to
telecommunications. Certain embodiments relate more particularly to
concepts such as long-term evolution (LTE), MulteFire, narrowband
internet-of-things (NB-IoT), unlicensed spectrum, and discovery
reference signals (DRSs).
BACKGROUND
[0002] In some telecommunications systems, a radio access node
transmits DRSs to allow wireless communication devices to identify
cells and/or measure radio resources, among other things. Examples
of such systems include Long Term Evolution (LTE) systems and
MulteFire systems.
[0003] A typical DRS may comprise, e.g. a primary synchronization
signal (PSS), a secondary synchronization signal (SSS), a
cell-specific reference signal (CRS), and/or other information.
Such a DRS may be transmitted periodically (e.g., within a periodic
DRS window) and have a specified duration or dwell time. Wireless
communication devices may therefore detect such a DRS according to
a configured DRS periodicity.
[0004] The details and/or requirements of DRS implementation may
vary according by context. For instance, DRS implementation may
vary between a NB-IoT system and a non-NB-IoT system, or between a
system operating in unlicensed spectrum (e.g., license assisted
access (LAA) enabled LTE system, or a MulteFire system) and a
system not operating in unlicensed spectrum. Consequently, there is
a general need for effective DRS designs that address specific
issues according to context.
SUMMARY
[0005] In certain embodiments of the disclosed subject matter, a
method of operating a wireless communication device comprises
receiving a narrowband secondary synchronization signal (NSSS) in a
discovery reference signal (DRS), identifying a transformation
applied to the NSSS, and determining a DRS periodicity based on the
identified transformation.
[0006] In certain related embodiments, identifying the
transformation comprises identifying a phase shift of the NSSS. In
some such embodiments, identifying the phase shift comprises
determining the phase shift from among a predetermined number of
candidate phase shift values, and wherein the DRS periodicity is
determined from among a predetermined number of candidate DRS
periodicities according to the determined phase shift. In some
embodiments the predetermined number of candidate phase shift
values is four and the predetermined number of candidate DRS
periodicities is four.
[0007] In certain related embodiments, identifying the
transformation comprises identifying an orthogonal cover code (OCC)
applied to the NSSS. In some such embodiments, identifying the OCC
comprises determining the OCC from among a predetermined number of
candidate OCCs, and wherein the DRS periodicity is determined from
among a predetermined number of candidate DRS periodicities
according to the determined OCC. In some such embodiments the
predetermined number of candidate OCCs is four and the
predetermined number of candidate DRS periodicities is four.
[0008] In certain related embodiments, the method further comprises
detecting a narrowband physical broadcast channel (NPBCH) within a
same DRS period as the NSSS. In some such embodiments, the method
further comprises identifying another transformation applied to the
NSSS, and determining a redundancy version of the NPBCH according
to the other transformation. In some such embodiments the
transformation is a phase shift, and the other transformation is an
orthogonal cover code (OCC). In certain alternative embodiments,
the transformation is an orthogonal cover code (OCC) and the other
transformation is a phase shift.
[0009] In certain related embodiments, the DRS is transmitted in
unlicensed spectrum.
[0010] In certain embodiments of the disclosed subject matter, a
wireless communication device comprises processing circuitry,
memory and transceiver circuitry collectively configured to receive
a narrowband secondary synchronization signal (NSSS) in a discovery
reference signal (DRS), identify a transformation applied to the
NSSS, and determine a DRS periodicity based on the identified
transformation.
[0011] In certain related embodiments, the processing circuitry,
memory and transceiver circuitry are collectively further
configured to detect a narrowband physical broadcast channel
(NPBCH) within a same DRS period as the NSSS. In some such
embodiments the processing circuitry, memory and transceiver
circuitry are collectively further configured to identify another
transformation applied to the NSSS, and determine a redundancy
version of the NPBCH according to the other transformation.
[0012] In certain related embodiments, the transformation is a
phase shift or an orthogonal cover code (OCC).
[0013] In certain embodiments of the disclosed subject matter, a
radio access node comprises processing circuitry, memory and
transceiver circuitry collectively configured to determine a
discovery reference signal (DRS) periodicity, apply a
transformation to a narrowband secondary synchronization signal
(NSSS) to be transmitted in a DRS, wherein the transformation
corresponds to the determined DRS periodicity, and transmit the
NSSS in the DRS. In some such embodiments, the transformation is a
phase shift or an orthogonal cover code (OCC). In certain
alternative embodiments, the processing circuitry, memory and
transceiver circuitry are further collectively configured to apply
another transformation to the NSSS, wherein the other
transformation corresponds to a redundancy version of a narrowband
physical broadcast channel (NPBCH) to be transmitted within a same
DRS period as the NSSS. In some such embodiments, the
transformation is a phase shift and the other transformation is an
orthogonal cover code (OCC).
[0014] Certain embodiments of the disclosed subject matter are
presented in recognition of shortcomings associated with
conventional techniques and technologies, such as the following
examples. For the designs currently under discussion within MFA,
having a configurable DRS periodicity is regarded as beneficial.
The benefit of having the DRS periodicity configurable is that
depending on deployment, the overhead can be adjusted and expected
latency can be adjusted to fit the needs of a specific deployment.
However, for the UE to be able to utilize several transmissions of
the NPBCH for reception, the periodicity of the DRS needs to be
derived before starting NPBCH reception. One option is to fix the
periodicity in the specification, which has the drawbacks of not
providing flexible deployment options.
[0015] Certain embodiments of the disclosed embodiments may provide
potential benefits compared to conventional techniques and
technologies, such as the following examples.
[0016] By using the phases of the NSSS, the DRS periodicity can be
made configurable, and still enables UEs to combine several
instances of the NPBCH for improved performance. Knowing the DRS
periodicity can save UE battery as the UE does not need multiple
attempts to derive the DRS periodicity and timing, the used RV can
be contained in the NSSS info. By enabling the DRS periodicity to
be configurable, the system can be adjusted to fit for example
different latency needs at a specific deployment.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The drawings illustrate selected embodiments of the
disclosed subject matter. In the drawings, like reference labels
denote like features.
[0018] FIG. (FIG.) 1 illustrates communication system according to
an embodiment of the disclosed subject matter.
[0019] FIG. 2A illustrates a wireless communication device
according to an embodiment of the disclosed subject matter.
[0020] FIG. 2B illustrates a wireless communication device
according to another embodiment of the disclosed subject
matter.
[0021] FIG. 3A illustrates a radio access node according to an
embodiment of the disclosed subject matter.
[0022] FIG. 3B illustrates a radio access node according to another
embodiment of the disclosed subject matter.
[0023] FIG. 4 illustrates a radio access node according to yet
another embodiment of the disclosed subject matter.
[0024] FIG. 5 illustrates an example DRS structure according to
some embodiments of the disclosed subject matter.
[0025] FIG. 6 illustrates an example of NPSS and NSSS
performance.
[0026] FIGS. 7A and 7B illustrate examples of NPBCH
performance.
[0027] FIG. 8 illustrates a method of operating a wireless
communication device according to an embodiment of the disclosed
subject matter.
[0028] FIG. 9 illustrates a method of operating a radio access node
according to an embodiment of the disclosed subject matter.
DETAILED DESCRIPTION
[0029] The following description presents various embodiments of
the disclosed subject matter. These embodiments are presented as
teaching examples and are not to be construed as limiting the scope
of the disclosed subject matter. For example, certain details of
the described embodiments may be modified, omitted, or expanded
upon without departing from the scope of the disclosed subject
matter.
[0030] LTE defines radio frames consisting of ten equally sized
subframes of 1 ms length. Each frame is identified by a System
Frame Number (SFN). The SFN is used to control different
transmission cycles that may have a period longer than one frame,
such as paging. The SFN supports 2.sup.10=1024 values corresponding
to 10.24 seconds.
[0031] The 8 most significant bits of the SFN are signaled in the
Master Information Block (MIB). The 2 least significant bits are
derived by decoding the Physical Broadcast Channel (PBCH). The PBCH
is transmitted with a transmit time interval (TTI) of 40 ms. Within
the PBCH TTI, 4 different redundancy versions (RVs) of the PBCH are
transmitted in SF#0 of each radio frame. Thus, one radio frame
within the PBCH TTI can be identified by the RV. In each radio
frame, SF#0 and SF#5 contain Secondary Synchronization Signal (SSS)
and Primary Synchronization Signal (PSS) of 1 orthogonal frequency
division multiplexing (OFDM) symbol length for frequency division
duplexing (FDD), and in SF#0 and SF#4 for time division duplexing
(TDD).
[0032] For NB-IoT, which supports single Physical Resource Block,
1-PRB (180 kHz) systems, coverage is extended by increasing the
TTIs and increasing the number of repetitions. This results in an
increased PBCH TTI of 640 ms, which is divided into eight blocks of
80 ms length. Each block is identified by one of 8 Code Subblock
(CSB) versions, and in each block, the same CSB version is
transmitted in SF#0 of each radio frame. Similarly, the narrowband
primary synchronization signal (NPSS) and narrowband secondary
synchronization signal (NSSS) are extended to 11 OFDM symbols, and
thus occupy the data region of 1 subframe.
[0033] NPSS is transmitted in SF#5 in each radio frame, and NSSS is
transmitted in SF#9 of every radio frame with even SFN. The
NPSS/NSSS have a period of 80 ms and allow the UE to establish
timing within this 80 ms period.
[0034] With the 8 CSB versions, it is possible to identify a block
within the NPBCH TTI. Within the 80 ms block, NPSS provides 10 ms
timing, and NSSS uses 4 different phases, which gives the 80 ms
timing information.
[0035] As a consequence, 6 bits for SFN are derived from
PBCH/NSSS/NPSS decoding (640 ms NPBCH TTI). The 4 MSBs of the SFN
are transmitted in MIB-NB.
[0036] Due to the expansion in time, the 10-bit Hyper System Frame
Number, also referred to as H-SFN or HFN, has been introduced to
identify SFN wrap-arounds.
[0037] For NB-IoT in unlicensed spectrum (NB-IoT-U), which is
currently being specified for MulteFire (MF) 1.1 for sub-1GHz bands
in the US/EU/China, NB-IoT-U shall comply with FCC regulations
(15.247) for the US. There are basically 3 design options.
[0038] A first option is Digital modulation (DM). DM requires usage
of 3 PRBs, which diverts from the original 1-PRB design.
[0039] A second option is frequency hopping spread spectrum (FHSS).
FHSS requires the system to hop over at least N=50 frequencies if
the bandwidth is <250 kHz. The system stays on each frequency
for a specific time referred to as the dwell time. The dwell time
is assumed to be a multiple of a radio frame. A frequency hopping
cycle (FH cycle) implies that each of the N hopping frequencies is
visited exactly once. Further, it is assumed that at least
synchronization signals are transmitted on one or more known
frequencies. These are referred to as anchor or discovery
channels.
[0040] According to MulteFire contributions mf2018.088.00 &
mf2018.067.00, for initial acquisition, a UE would only monitor the
primary discovery channel, which only occurs every N frequency
hops. Here, it is assumed that the P-Channel contains NPSS, NSSS,
and NPBCH for one-shot acquisition.
[0041] A third option is a hybrid system. A hybrid system may
assume DM for initial acquisition, and FH for data
transmission/reception. The dwell time on each frequency depends on
the design, but mainly depends on the NPSS/NSSS synchronization
performance and potentially NPBCH performance and whether to aim
for one-shot or accumulated acquisition. For the hybrid system, we
consider only one discovery channel, which may be visited more
often than just once per FH cycle (see e.g. mf2018.338.00).
[0042] For a DRS repetition factor of 2, the DRS periodicity is the
FH cycle duration divided by a factor of 2. In some embodiments,
the dwell duration is 20 ms, and the number of hopping positions is
N=64, resulting in a FH cycle 64*20 ms=1280 ms.
[0043] With a DRS repetition factor of {1, 2, 4, 8, 16, etc.}, the
DRS period would be {1280 ms, 640 ms, 320 ms, 160 ms, 80 ms}. If
the FH cycle duration shall be fixed to 64*20 ms=1280 ms, the DRS
transmission will puncture frequency hops.
[0044] For DRS period=1280 ms, the DRS repetition factor DRS_rep
would be 1, and thus the number of frequency hops would be
N=64-DRS_rep=63. For DRS period=320 ms, i.e the DRS repetition
factor is 1280 ms/320 ms=4, meaning that 4 hops within the FH cycle
would be punctured out, i.e. N=(64-DRS rep)=60.
[0045] For DRS_rep=2, N=62 hopping frequencies. For DRS_rep=4, N=60
hopping frequencies. And for DRS rep=8, N=56 hopping
frequencies.
[0046] In some NB-IoT designs, a narrowband secondary NSSS encodes
timing information by encoding the NSSS with different phase
shifts. Depending on the frequency hopping and frame-structure
design of NB-IoT-U, timing information in NSSS may not be needed,
and the phase shifts used for NSSS are free to use for other
purposes.
[0047] There are four phase shifts for NSSS defined for NB-IoT-U,
and these can be used to convey DRS periodicity information to the
UE. It is deemed sufficient with four periodicities to get a
flexible NB-IoT-U system.
[0048] The user equipment (UE) steps are for such a process may be
as follows. Detect an NSSS (step 1), determine the phase shift of
the NSSS (step 2), and determine the DRS periodicity based on the
phase shift (step 3). Such a process may further comprise searching
or detecting and reading a broadcast channel (e.g. NPBCH) for
further system information regarding the cell access such as
barring and random access information (step 4).
[0049] To help the UE with the NPBCH decoding process, 4 cover
codes (CC) could additionally be used and associated with the 8
redundancy version (RV) of the NPBCH (step 5). In one example, a CC
0 is associated with RV mod4=0, a CC 1 is associated with RV mod
4=1. A CC 2 is associated with RV mod=2, and a CC 3 is associated
with RV mod 4. Instead of 8 decoding hypothesis, the UE only has to
try 2 hypotheses. Alternatively, in step 2, the 4 cover codes can
be used instead of the phase shift to signal the 4 DRS
periodicities, and in step 5, the phase shift can be used instead
of the CC.
[0050] As indicated by the foregoing, in certain embodiments a
network node (e.g., an eNB or gNB) transmits an NSSS signal, using
the phase of the NSSS to convey to the UE the periodicity of the
DRS. A related solution from a UE perspective is to receive the
NSSS, determine the DRS periodicity from the NSSS phase shift
information, and perform NPBCH reception with the possibility to
combine over several instances of the NPBCH.
[0051] A NB-IoT NSSS for a cell can be determined by a Zadoff Chu
sequence, 4 cover codes and 4 phase shifts. This allows for 504
PCIDs determined by the ZC sequence and the 4 cover codes.
[0052] In the unlicensed operation using FH, the NSSS along with
the NPSS occurs once every N_DRS hops on the discovery channel on a
specified frequency, as in the following example. [0053] FH cycle
[0054] Tdwell=20 ms [0055] N_DRS=16 hops [0056] .ltoreq.DRS
period=320 ms
[0057] Because the NSSS periodicity is 320 ms, the 4 phase shifts
used to determine the timing within 80 ms is not required. In
certain embodiments described herein, the 4 values of the phase
shift are used to determine the DRS periodicity (DRS
period=N_DRS*20 ms).
[0058] After determining the DRS periodicity, the UE continues to
decode the NPBCH which can use the same or a different format as
existing systems.
[0059] The described embodiments may be implemented in any
appropriate type of communication system supporting any suitable
communication standards and using any suitable components. As one
example, certain embodiments may be implemented in a communication
system such as that illustrated in FIG. 1. Although certain
embodiments are described with respect to LTE systems and related
terminology, the disclosed concepts are not limited to LTE or a
3GPP system. Additionally, although reference may be made to the
term "cell", the described concepts may also apply in other
contexts, such as beams used in Fifth Generation (5G) systems, for
instance.
[0060] Referring to FIG. 1, a communication system 100 comprises a
plurality of wireless communication devices 105 (e.g., UEs, machine
type communication [MTC]/machine-to-machine [M2M] UEs) and a
plurality of radio access nodes 110 (e.g., eNodeBs or other base
stations). Communication system 100 is organized into cells 115,
which are connected to a core network 120 via corresponding radio
access nodes 110. Radio access nodes 110 are capable of
communicating with wireless communication devices 105 along with
any additional elements suitable to support communication between
wireless communication devices or between a wireless communication
device and another communication device (such as a landline
telephone).
[0061] Although wireless communication devices 105 may represent
communication devices that include any suitable combination of
hardware and/or software, these wireless communication devices may,
in certain embodiments, represent devices such as those illustrated
in greater detail by FIGS. 2A and 2B. Similarly, although the
illustrated radio access node may represent network nodes that
include any suitable combination of hardware and/or software, these
nodes may, in particular embodiments, represent devices such those
illustrated in greater detail by FIGS. 3A, 3B and 4.
[0062] Referring to FIG. 2A, a wireless communication device 200A
comprises a processor 205 (e.g., Central Processing Units [CPUs],
Application Specific Integrated Circuits [ASICs], Field
Programmable Gate Arrays [FPGAs], and/or the like), a memory 210, a
transceiver 215, and an antenna 220. In certain embodiments, some
or all of the functionality described as being provided by UEs, MTC
or M2M devices, and/or any other types of wireless communication
devices may be provided by the device processor executing
instructions stored on a computer-readable medium, such as memory
210. Alternative embodiments may include additional components
beyond those shown in FIG. 2A that may be responsible for providing
certain aspects of the device's functionality, including any of the
functionality described herein.
[0063] Referring to FIG. 2B, a wireless communication device 200B
comprises at least one module 225 configured to perform one or more
corresponding functions. Examples of such functions include various
method steps or combinations of method steps as described herein
with reference to wireless communication device(s). In general, a
module may comprise any suitable combination of software and/or
hardware configured to perform the corresponding function. For
instance, in some embodiments a module comprises software
configured to perform a corresponding function when executed on an
associated platform, such as that illustrated in FIG. 2A.
[0064] Referring to FIG. 3A, a radio access node 300A comprises a
control system 320 that comprises a node processor 305 (e.g.,
Central Processing Units (CPUs), Application Specific Integrated
Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and/or
the like), memory 310, and a network interface 315. In addition,
radio access node 300A comprises at least one radio unit 325
comprising at least one transmitter 335 and at least one receiver
coupled to at least one antenna 330. In some embodiments, radio
unit 325 is external to control system 320 and connected to control
system 320 via, e.g., a wired connection (e.g., an optical cable).
However, in some other embodiments, radio unit 325 and potentially
the antenna 330 are integrated together with control system 320.
Node processor 305 operates to provide at least one function 345 of
radio access node 300A as described herein. In some embodiments,
the function(s) are implemented in software that is stored, e.g.,
in the memory 310 and executed by node processor 305.
[0065] In certain embodiments, some or all of the functionality
described as being provided by a base station, a node B, an enodeB,
and/or any other type of network node may be provided by node
processor 305 executing instructions stored on a computer-readable
medium, such as memory 310 shown in FIG. 3A. Alternative
embodiments of radio access node 300 may comprise additional
components to provide additional functionality, such as the
functionality described herein and/or related supporting
functionality.
[0066] Referring to FIG. 3B, a radio access node 300B comprises at
least one module 350 configured to perform one or more
corresponding functions. Examples of such functions include various
method steps or combinations of method steps as described herein
with reference to radio access node(s). In general, a module may
comprise any suitable combination of software and/or hardware
configured to perform the corresponding function. For instance, in
some embodiments a module comprises software configured to perform
a corresponding function when executed on an associated platform,
such as that illustrated in FIG. 3A.
[0067] FIG. 4 is a block diagram that illustrates a virtualized
radio access node 400 according to an embodiment of the disclosed
subject matter. The concepts described in relation to FIG. 4 may be
similarly applied to other types of network nodes. Further, other
types of network nodes may have similar virtualized architectures.
As used herein, the term "virtualized radio access node" refers to
an implementation of a radio access node in which at least a
portion of the functionality of the radio access node is
implemented as a virtual component(s) (e.g., via a virtual
machine(s) executing on a physical processing node(s) in a
network(s)).
[0068] Referring to FIG. 4, radio access node 400 comprises control
system 320 as described in relation to FIG. 3A.
[0069] Control system 320 is connected to one or more processing
nodes 420 coupled to or included as part of a network(s) 425 via
network interface 315. Each processing node 420 comprises one or
more processors 405 (e.g., CPUs, ASICs, FPGAs, and/or the like),
memory 410, and a network interface 415.
[0070] In this example, functions 345 of radio access node 300A
described herein are implemented at the one or more processing
nodes 420 or distributed across control system 320 and the one or
more processing nodes 420 in any desired manner. In some
embodiments, some or all of the functions 345 of radio access node
300A described herein are implemented as virtual components
executed by one or more virtual machines implemented in a virtual
environment(s) hosted by processing node(s) 420. As will be
appreciated by one of ordinary skill in the art, additional
signaling or communication between processing node(s) 420 and
control system 320 is used in order to carry out at least some of
the desired functions 345. As indicated by dotted lines, in some
embodiments control system 320 may be omitted, in which case the
radio unit(s) 325 communicate directly with the processing node(s)
420 via an appropriate network interface(s).
[0071] In some embodiments, a computer program comprises
instructions which, when executed by at least one processor, causes
at least one processor to carry out the functionality of a radio
access node (e.g., radio access node 110 or 300A) or another node
(e.g., processing node 420) implementing one or more of the
functions of the radio access node in a virtual environment
according to any of the embodiments described herein.
[0072] FIG. 5 illustrates an example DRS structure according to
some embodiments of the disclosed subject matter. As illustrated in
FIG. 5, the DRS structure comprises NPSS, NSSS and NPBCH. In
certain embodiments described herein, once a wireless communication
device detects the NSSS has been detected, it can thereafter try to
decode the subsequent NPBCH.
[0073] The following description presents investigations of the
performance of such a 20 ms DRS (NSSS, NPSS and NPBCH) signal when
using Digital Modulation (DM) and mapping the NSSS, NPSS and NPBCH
on one out of three available PRBs.
[0074] FIG. 6 illustrates an example of NPSS and NSSS performance.
With a DM design the NPSS, NSSS synchronization must cope with a
SINR operating point of -13.3 dB to support a MPL of 161 dB. FIG. 6
shows the single shot BLER performance.
[0075] The NPSS uses a length 8.times.14 cover code. The NSSS is
extended to cover 14 OFDM symbols using a design that follows the
following principles:
[0076] A 167 length ZC sequence is mapped over 14 OFDM symbols. A
cyclic extension is used to generate a length 168 sequence.
[0077] 126 ZC roots are used to generate 126 sequences.
[0078] 4 different 168 length truncated Hadamard based cover codes
is applied onto the ZC sequences to generate 504 sequences.
[0079] Each sequence is modulated with 4 different phases to
generate 504.times.4 sequences.
[0080] As illustrated in FIG. 6, at a signal-to-noise ratio (SNR)
of -13.3 dB the achieved BLER is 49%. After 4 independent attempts
a device can be assumed to achieve a BLER<10%.
[0081] FIGS. 7A and 7B illustrate examples of NPBCH performance.
With a DM design the NPBCH must cope with a SINR operating point of
-13.3 dB to support a MPL of 161 dB.
[0082] This example shows the performance for a design with the
following characteristics:
[0083] 14 OFDM symbols/subframe
[0084] 2 NRS ports, and 12 NRS per port.
[0085] 3 dB NRS power boosting.
[0086] 8 code blocks, each containing 10 repetitions.
[0087] FIG. 7A shows the BLER performance when we configure
T.sub.period=80 ms code block periodicity. As illustrated in FIG.
7A, at a SNR of -13.3 dB the achieved BLER is well below 10% after
the acquisition of 8 code blocks as shown in FIG. 7B.
[0088] In certain embodiments, DRS design may have the following
characteristics.
[0089] The NPSS may be extended to cover 14 OFDM symbols a use a
length 8x14 cover code.
[0090] The NSSS may be extended to cover 14 OFDM symbols using a
design that follows the following principles. [0091] A 167 length
ZC sequence is mapped over 14 OFDM symbols. A cyclic extension is
used to generate a length 168 sequence. [0092] 126 ZC roots are
used to generate 126 sequences. [0093] 4 different 168 length
truncated Hadamard based cover codes is applied onto the ZC
sequences to generate 504 sequences. [0094] Each sequence is
modulated with 4 different phases to generate
504.times.4sequences.
[0095] The NPBCH may be extended to cover 14 OFDM symbols using a
design that follows the following principles. [0096] Specify
support for up to 2 NRS ports, with 12 NRS per port. [0097] Specify
support for up to 3 dB NRS power boosting. [0098] The NPBCH is
encoded into 8 code blocks, each containing 10 repetitions and
mapped to 10 consecutive subframes.
[0099] In some embodiments, a DRS may also be designed according to
the following.
[0100] The NPSS may be extended to cover 14 OFDM symbols a use a
length 8.times.14 cover code.
[0101] The NSSS may be extended to cover 14 OFDM symbols using a
design according to the following principles. [0102] A 167 length
ZC sequence is mapped over 14 OFDM symbols. A cyclic extension is
used to generate a length 168 sequence. [0103] 126 ZC roots are
used to generate 126 sequences. [0104] 4 different 168 length
truncated Hadamard based cover codes is applied onto the ZC
sequences to generate 504 sequences. [0105] Each sequence is
modulated with 4 different phases to generate 504x4 sequences.
[0106] The NPBCH may be extended to cover 14 OFDM symbols using a
design according to the following. [0107] Specify support for up to
2 NRS ports, with 12 NRS per port. [0108] Specify support for up to
3 dB NRS power boosting. [0109] The NPBCH is encoded into 8 code
blocks, each containing 10 repetitions and mapped to 10 consecutive
subframes.
[0110] In some embodiments, total initial NPSS, NSSS, NPBCH
acquisition time may be defined in relation to one or more of the
following characteristics.
[0111] If the NPSS, NSSS and NPBCH appears with a periodicity of
T.sub.period ms it has been shown that synchronization targeting
10% BLER can be achieved after roughly
T.sub.tot=5.times.T.sub.period+8.times.T.sub.period ms. [0112]
Assuming T.sub.period=80 ms gives T.sub.tot=1.04 s [0113] Assuming
T.sub.period=160 ms gives T.sub.tot=2.08 s [0114] Assuming
T.sub.period=320 ms gives T.sub.tot=4.16 s [0115] Assuming
T.sub.period=640 ms gives T.sub.tot=8.32 s [0116] Assuming
T.sub.period=1280 ms gives T.sub.tot=16.64 s
[0117] In general, supporting a configurable periodicity may offer
a beneficial tradeoff between latency and NPSS, NSSS, NPBCH
overhead.
[0118] An NPBCH design may have 8 code blocks, each containing 10
repetitions as illustrated in FIG. 5 with T.sub.period configurable
and selected from the set of 4 DRS periods.
[0119] The chosen T.sub.period may be signaled using the NSSS phase
or an OCC code, for instance.
[0120] In various embodiments as described herein, a 20 ms DRS
structure can be used in a digital modulated system.
[0121] In certain embodiments, the NPSS is extended to cover 14
OFDM symbols and use a length 8.times.14 cover code.
[0122] In certain embodiments, the NSSS is extended to cover 14
OFDM symbols using a design according to the following. [0123] A
167 length ZC sequence is mapped over 14 OFDM symbols. A cyclic
extension is used to generate a length 168 sequence. [0124] 126 ZC
roots are used to generate 126 sequences. [0125] 4 different 168
length truncated Hadamard based cover codes is applied onto the ZC
sequences to generate 504 sequences. [0126] Each sequence is
modulated with 4 different phases to generate 504.times.4
sequences.
[0127] In some embodiments, the NPBCH is extended to cover 14 OFDM
symbols using a design according to the following. [0128] Specify
support for up to 2 NRS ports, with 12 NRS per port. [0129] Specify
support for up to 3 dB NRS power boosting. [0130] The NPBCH is
encoded into 8 code blocks, each containing 10 repetitions and
mapped to 10 consecutive subframes.
[0131] In some embodiments, an NPBCH comprises 8 code blocks, each
containing 10 repetitions as shown in FIG. 5, with T.sub.period
configurable and selected from the set of 4 DRS periods. The chosen
T.sub.period can an be signaled using the NSSS phase or orthogonal
cover code, for example.
[0132] FIG. 8 illustrates a method of operating a wireless
communication device according to an embodiment of the disclosed
subject matter. The method could be performed, for instance, by a
wireless communication device as described in relation to any of
FIGS. 1-2 and 4. Such a wireless communication device could
comprise processing circuitry, memory and transceiver circuitry
collectively configured to perform the operations of the method,
such as those described below.
[0133] Referring to FIG. 8, the method comprises receiving a
narrowband secondary synchronization signal (NSSS) in a discovery
reference signal (DRS) (S805), identifying a transformation applied
to the NSSS (S810), and determining a DRS periodicity based on the
identified transformation (S815).
[0134] The transformation may comprise, for instance, a phase shift
of the NSSS. The phase shift may be determined from among a
predetermined number of candidate phase shift values, and the DRS
periodicity is determined from among a predetermined number of
candidate DRS periodicities according to the determined phase
shift. For instance, the predetermined number of candidate phase
shift values may be four and the predetermined number of candidate
DRS periodicities may be four. The four DRS periodicities could be
selected from a set of five options as described herein, although
they are not limited thereto.
[0135] In an alternative embodiment, the transformation may
comprise an orthogonal cover code (OCC). The wireless communication
device may, for instance, identify the OCC from among a
predetermined number of candidate OCCs, and the DRS periodicity may
be determined from among a predetermined number of candidate DRS
periodicities according to the determined OCC. In some embodiments,
the predetermined number of candidate OCCs is four and the
predetermined number of candidate DRS periodicities is four.
[0136] In some embodiments, the method of FIG. 8 further comprises
detecting a narrowband physical broadcast channel (NPBCH) within a
same DRS period as the NSSS. The method may still further comprise
identifying another transformation applied to the NSSS, and
determining a redundancy version of the NPBCH according to the
other transformation. In one example, the transformation is a phase
shift, and the other transformation is an orthogonal cover code
(OCC). In certain embodiments, the transformation is an orthogonal
cover code (OCC) and the other transformation is a phase shift.
[0137] In the method of FIG. 8, as well as in other embodiments,
the DRS may be transmitted in unlicensed spectrum. For instance,
the DRS may be transmitted in an LAA enabled LTE system, a
MulteFire system, or another type of system operating in unlicensed
spectrum.
[0138] FIG. 9 illustrates a method of operating a radio access node
according to an embodiment of the disclosed subject matter. The
method could be performed, for instance, by a radio access node as
described in relation to any of FIGS. 1 and 3-4. Such a wireless
communication device could comprise processing circuitry, memory,
transceiver circuitry, and/or other features collectively
configured to perform the operations of the method, such as those
described below.
[0139] Referring to FIG. 9, the method comprises determining a
discovery reference signal (DRS) periodicity (S905), applying a
transformation to a narrowband secondary synchronization signal
(NSSS) to be transmitted in a DRS, wherein the transformation
corresponds to the determined DRS periodicity (S910), and
transmitting the NSSS in the DRS (S915). The transformation could
be, for instance, a phase shift or an orthogonal cover code
(OCC).
[0140] In some embodiments, the method further comprises applying
another transformation to the NSSS, wherein the other
transformation corresponds to a redundancy version of a narrowband
physical broadcast channel (NPBCH) to be transmitted within a same
DRS period as the NSSS. The transformation may be e.g. a phase
shift and the other transformation is an orthogonal cover code
(OCC).
[0141] In addition to the foregoing features, the method of FIG. 9
may also include features such as signal characteristics and
transformations as described in relation to the method of FIG. 8.
Moreover, various methods or apparatuses as described above,
including those of FIGS. 8 and 9, may incorporate details such as
DRS structures, timing information, protocols, block
configurations, etc., as described above.
[0142] While the disclosed subject matter has been presented above
with reference to various embodiments, it will be understood that
various changes in form and details may be made to the described
embodiments without departing from the overall scope of the
disclosed subject matter.
* * * * *